12021997891 has 2 divisors, whose sum is σ = 12021997892. Its totient is φ = 12021997890.

The previous prime is 12021997853. The next prime is 12021997973. The reversal of 12021997891 is 19879912021.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 12021997891 - 2²⁵ = 11988443459 is a prime.

It is not a weakly prime, because it can be changed into another prime (12021997391) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 6010998945 + 6010998946.

It is an arithmetic number, because the mean of its divisors is an integer number (6010998946).

Almost surely, 2^12021997891 is an apocalyptic number.

12021997891 is a deficient number, since it is larger than the sum of its proper divisors (1).

12021997891 is an equidigital number, since it uses as much as digits as its factorization.

12021997891 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 163296, while the sum is 49.

The spelling of 12021997891 in words is "twelve billion, twenty-one million, nine hundred ninety-seven thousand, eight hundred ninety-one".